نتایج جستجو برای: cosmic microwave background cmb

تعداد نتایج: 905952  

1999
Aparna Venkatesan APARNA VENKATESAN

Current data of high-redshift absorption-line systems imply that hydrogen reionization occurred before redshifts of about 5. Previous works on reionization by the Ðrst stars or quasars have shown that such scenarios are described by a large number of cosmological and astrophysical parameters. Here we adopt a semianalytic model of stellar reionization in order to quantify how the optical depth t...

2008
M. LIGUORI L. MOSCARDINI

We describe a new numerical algorithm to obtain high-resolution simulated maps of the Cosmic Microwave Background (CMB), for a broad class of non-Gaussian models. The kind of non-Gaussianity we account for is based on the simple idea that the primordial gravitational potential is obtained by a non-linear but local mapping from an underlying Gaussian random field, as resulting from a variety of ...

2005
D. Menzies G. J. Mathews

Recent studies have found the earth's peculiar velocity to be significant in microwave background based tests for compact cosmic topology, and modifications to these tests have been proposed. Tests of non-gaussianity, weak lensing analysis and new tests using improved CMB data will also be sensitive to peculiar velocity. We propose here to simplify matters by showing how to construct a deaberra...

2008
Adrienne L. Erickcek Sean M. Carroll Marc Kamionkowski

Superhorizon perturbations induce large-scale temperature anisotropies in the cosmic microwave background (CMB) via the Grishchuk-Zel’dovich effect. We analyze the CMB temperature anisotropies generated by a single-mode adiabatic superhorizon perturbation. We show that an adiabatic superhorizon perturbation in a CDM universe does not generate a CMB temperature dipole, and we derive constraints ...

2008
Yen-Ting Lin Benjamin D. Wandelt

We present here a detailed, self–contained treatment of the mathematical formalism for describing the theory of polarized anisotropy in the cosmic microwave background. This didactic review is aimed at researchers who are new to the field. We first develop the mathematical tools for describing polarized scattering of CMB photons. Then we take the reader through a detailed derivation of the line...

2009
Franz Elsner Benjamin D. Wandelt

We describe an algorithm to generate temperature and polarization maps of the cosmic microwave background radiation containing non–Gaussianity of arbitrary local type. We apply an optimized quadrature scheme that allows us to predict and control integration accuracy, speed up the calculations, and reduce memory consumption by an order of magnitude. We generate 1000 non– Gaussian CMB temperature...

2003
Louise M. Griffiths

Under the assumption that the concordance Λ cold dark matter (CDM) model is the correct model, we test the cosmic microwave background (CMB) anisotropy data for systematic effects by examining the band pass temperature residuals with respect to this model. Residuals are analysed as a function of angular scale l, galactic latitude, frequency, calibration source, instrument type and several other...

2005
J. JIN

Higher Criticism is a statistic recently proposed by Donoho and Jin5. It has been shown to be effective in resolving a very subtle testing problem: whether n normal means are all zero versus a small fraction is nonzero. Higher Criticism is also useful for non-Gaussian detection in Cosmic Microwave Background (CMB) data. In this report, we review the theory developed in Donoho and Jin5 and discu...

2008
David Coulson Neil Turok

Abstract The COBE satellite’s maps of the cosmic microwave background (CMB) anisotropy do not have the resolution to discriminate between theories of cosmic structure formation based on inflation, and those based on field ordering following a symmetry breaking phase transition. For this purpose it is critical to resolve the CMB anisotropy on degree scales. In this paper we report on detailed ca...

1997
M. Kamionkowski

Inflation provides a unified paradigm for understanding the isotropy of the cosmic microwave background (CMB), the flatness problem, and the origin of large-scale structure. Although the physics responsible for inflation is not yet well understood, slow-roll inflation generically makes several predictions: a flat Universe, primordial adiabatic density perturbations, and a stochastic gravity-wav...

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